Currently, transmission optical photolithography is used to form patterned layers in semiconductor manufacturing. Since the ability to resolve the semiconductor device features during photolithography is directly proportional to the wavelength of the light source, the wavelength of the light source needs to decrease as device dimensions decrease. To pattern device dimensions less than approximately 70 nanometers, one option is to use a light source with a wavelength in the extreme ultra-violet (EUV) regime. As used herein, the EUV regime has a characteristic wavelength between approximately 4-25 nanometers and more specifically, between 13-14 nanometers. Since it is difficult to find a material that transmits EUV radiation when exposed to wavelengths in the EUV regime, EUV lithography operates in a reflective mode as opposed to the transmission mode. Hence, EUV masks are reflective in nature and are not transmissive like the masks for optical photolithography or other technology options such as electron projection lithography or ion projection lithography.
Typically, an additive process is performed to fabricate an EUV mask. In this process, layers are formed and patterned over a reflective layer, which is formed on a mask substrate. Each additional layer that is formed and patterned requires deposition and patterning processes that increase the complexity of manufacturing the EUV mask. Thus, a need exists for an EUV mask that is capable of patterning small device features on a semiconductor wafer that is formed by a simplified manufacturing process.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve the understanding of the embodiments of the present invention.